Method and apparatus for improved color correction

Abstract

Methods and apparatuses for performing gamma corrections to maintain a plurality of colors substantially consistent with a color point. In one aspect of the present invention, a method to generate correction functions for performing color correction for a device for signals of different color components in a color space includes: generating a first correction function for a first color component in the color space; and generating second correction functions for second color components in the color space by reducing first color differences between a target white point and white points of a plurality of grays corrected by the first and second correction functions. The second color components are the color components in the color space other than the first color component. The first color differences are minimized relative to a chromaticity diagram.

1. A method to generate correction functions for performing color correction for a device for signals of different color components in a color space, the method comprising:
 generating a first correction function for a first color component in the color space; and  
 generating, according to the first correction function, second correction functions for second color components in the color space by reducing first color differences between a target white point and white points of a plurality of grays corrected by the first and second correction functions, the second color components including all color components in the color space except the first color component.  
 
   
   
     2. A method as in  claim 1  wherein the device is a color producing device; wherein the first correction function is computed based on at least one native transfer function of the device; and wherein the plurality of grays are colors produced by the device. 
   
   
     3. A method as in  claim 1  wherein the device is a color sensing device; and wherein the plurality of grays are colors being quantified by the device. 
   
   
     4. A method as in  claim 1  wherein the first color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     5. A method as in  claim 1  wherein the first correction function for the first color component is generated for gamma correction in the presence of signals for the first color component and in the absence of signals for the second color components. 
   
   
     6. A method as in  claim 5  wherein the first color component is Green in a RGB color space. 
   
   
     7. A method as in  claim 1  wherein the first correction function for the first color component is generated for gamma correction for luminance in the presence of signals for color components of the plurality of grays. 
   
   
     8. A method as in  claim 1  further comprising:
 determining third functions of the second color components as functions of the first color component by reducing second color differences between a target white point and white points corresponding to the first color components of different magnitudes and the second color components as determined by the third functions.  
 
   
   
     9. A method as in  claim 8  wherein the second color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     10. A method as in  claim 8  wherein said generating the second correction functions comprises:
 combining the first correction function and the third functions to generate the second correction functions.  
 
   
   
     11. A method to perform color correction for a device for signals of different color components in a color space, the method comprising:
 applying a first correction function to a first color component in the color space; and  
 applying second correction functions to second color components in the color space, the second correction functions being such that first color differences between a target white point and white points of a plurality of grays corrected by the first and second correction functions are reduced, the second color components including all color components of the color space except the first color component;  
 wherein said second correction functions are generated, according to the first correction function, by reducing first color difference between said target white point and the white points of the plurality of grays corrected by the first and second correction functions.  
 
   
   
     12. A method as in  claim 11  wherein the first color differences are reduced through computation relative to a chromaticity diagram. 
   
   
     13. A method as in  claim 11  wherein the first correction function for the first color component is for gamma correction in the presence of signals for the first color component and in the absence of signals for the second color components. 
   
   
     14. A method as in  claim 13  wherein the first color component is Green in a RGB color space. 
   
   
     15. A method as in  claim 11  wherein the first correction function for the first color component is for gamma correction for luminance in the presence of signals for color components of the plurality of grays. 
   
   
     16. A machine readable media containing data specifying correction functions for performing color correction for a device for signals of different color components in a color space, said correction functions produced by a method comprising:
 generating a first correction function for a first color component in the color space; and  
 generating, according to the first correction function, second correction functions for second color components in the color space by reducing first color differences between a target white point and white points of a plurality of grays corrected by the first and second correction functions, the second color components including all color components of the color space except the first color component.  
 
   
   
     17. A media as in  claim 16  wherein the device is a color producing device; and wherein the plurality of grays are colors produced by the device; and wherein the data in said media causes said device to maintain a substantially consistent white point over a plurality of gray levels from a white to a black. 
   
   
     18. A media as in  claim 16  wherein the device is a color sensing device; and wherein the plurality of grays are colors being quantified by the device. 
   
   
     19. A media as in  claim 16  wherein the first color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     20. A media as in  claim 16  wherein the first correction function for the first color component is generated for gamma correction in the presence of signals for the first color component and in the absence of signals for the second color components. 
   
   
     21. A media as in  claim 20  wherein the first color component is Green in a RGB color space. 
   
   
     22. A media as in  claim 16  wherein the first correction function for the first color component is generated for gamma correction for luminance in the presence of signals for color components of the plurality of grays. 
   
   
     23. A media as in  claim 16  wherein the method further comprises:
 determining third functions of the second color components as functions of the first color component by reducing second color differences between a target white point and white points corresponding to the first color components of different magnitudes and the second color components as determined by the third functions.  
 
   
   
     24. A media as in  claim 23  wherein the second color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     25. A media as in  claim 23  wherein said generating the second correction functions comprises:
 combining the first correction function and the third functions to generate the second correction functions.  
 
   
   
     26. A machine readable media containing executable computer program instructions which when executed by a digital processing system cause said system to perform a method to generate correction functions for performing color correction for a device for signals of different color components in a color space, the method comprising:
 generating a first correction function for a first color component in the color space; and  
 generating, according to the first correction function, second correction functions for second color components in the color space by reducing first color differences a target white point and white points of a plurality of grays corrected by the first and second correction functions, the second color components including all color components of the color space except the first color component.  
 
   
   
     27. A media as in  claim 26  wherein the device is a color producing device; and wherein the plurality of grays are colors produced by the device. 
   
   
     28. A media as in  claim 26  wherein the device is a color sensing device; and wherein the plurality of grays are colors being quantified by the device. 
   
   
     29. A media as in  claim 26  wherein the first color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     30. A media as in  claim 26  wherein the first correction function for the first color component is generated for gamma correction in the presence of signals for the first color component and in the absence of signals for the second color components. 
   
   
     31. A media as in  claim 30  wherein the first color component is Green in a RGB color space. 
   
   
     32. A media as in  claim 26  wherein the first correction function for the first color component is generated for gamma correction for luminance in the presence of signals for color components of the plurality of grays. 
   
   
     33. A media as in  claim 26  wherein the method further comprises:
 determining third functions of the second color components as functions of the first color component by reducing second color differences between a target white point and white points corresponding to the first color components of different magnitudes and the second color components as determined by the third functions.  
 
   
   
     34. A media as in  claim 33  wherein the second color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     35. A media as in  claim 33  wherein said generating the second correction functions comprises:
 combining the first correction function and the third functions to generate the second correction functions.  
 
   
   
     36. A machine readable media containing executable computer program instructions which when executed by a digital processing system cause said system to perform a method to perform color correction for a device for signals of different color components in a color space, the method comprising:
 applying a first correction function to a first color component in the color space; and  
 applying second correction functions to second color components in the color space, the second correction functions being such that first color differences between a target white point and white points of a plurality of grays corrected by the first and second correction functions are reduced, the second color components including all color components of the color space except the first color component;  
 wherein said second correction functions are generated, according to the first correction function, by reducing first color difference between said target white point and the white points of the plurality of grays corrected by the first and second correction functions.  
 
   
   
     37. A media as in  claim 36  wherein the first color differences are reduced through computation relative to a chromaticity diagram. 
   
   
     38. A media as in  claim 36  wherein the first correction function for the first color component is for gamma correction in the presence of signals for the first color component and in the absence of signals for the second color components. 
   
   
     39. A media as in  claim 38  wherein the first color component is Green in a RGB color space. 
   
   
     40. A media as in  claim 36  wherein the first correction function for the first color component is for gamma correction for luminance in the presence of signals for color components of the plurality of grays. 
   
   
     41. A digital processing system to generate correction functions for performing color correction for a device for signals of different color components in a color space, the digital processing system comprising:
 means for generating a first correction function for a first color component in the color space; and  
 means for generating, according to the first correction function, second correction functions for second color components in the color space by reducing first color differences between a target white point and white points of a plurality of grays corrected by the first and second correction functions, the second color components including all color components in the color space except the first color component.  
 
   
   
     42. A digital processing system as in  claim 41  wherein the device is a color producing device; and wherein the plurality of grays are colors produced by the device. 
   
   
     43. A digital processing system as in  claim 41  wherein the device is a color sensing device; and wherein the plurality of grays are colors being quantified by the device. 
   
   
     44. A digital processing system as in  claim 41  wherein the first color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     45. A digital processing system as in  claim 41  wherein the first correction function for the first color component is generated for gamma correction in the presence of signals for the first color component and in the absence of signals for the second color components. 
   
   
     46. A digital processing system as in  claim 45  wherein the first color component is Green in a RGB color space. 
   
   
     47. A digital processing system as in  claim 41  wherein the first correction function for the first color component is generated for gamma correction for luminance in the presence of signals for color components of the plurality of grays. 
   
   
     48. A digital processing system as in  claim 41  further comprising:
 means for determining third functions of the second color components as functions of the first color component by reducing second color differences between a target white point and white points corresponding to the first color components of different magnitudes and the second color components as determined by the third functions.  
 
   
   
     49. A digital processing system as in  claim 48  wherein the second color differences are minimized through computation relative to a chromaticity diagram. 
   
   
     50. A digital processing system as in  claim 48  wherein said means for generating the second correction functions comprises:
 means for combining the first correction function and the third functions to generate the second correction functions.  
 
   
   
     51. A digital processing system to perform color correction for a device for signals of different color components in a color space, the digital processing system comprising:
 means for applying a first correction function to a first color component in the color space; and  
 means for applying second correction functions to second color components in the color space, the second correction functions being such that first color differences between a target white point and white points of a plurality of grays corrected by the first and second correction functions are reduced, the second color components including all color components of the color space except the first color component;  
 wherein said second correction functions are generated, according to the first correction function, by reducing first color difference between said target white point and the white points of the plurality of grays corrected by the first and second correction functions.  
 
   
   
     52. A digital processing system as in  claim 51  wherein the first color differences are reduced through computation relative to a chromaticity diagram. 
   
   
     53. A digital processing system as in  claim 51  wherein the first correction function for the first color component is for gamma correction in the presence of signals for the first color component and in the absence of signals for the second color components. 
   
   
     54. A digital processing system as in  claim 53  wherein the first color component is Green in a RGB color space. 
   
   
     55. A digital processing system as in  claim 51  wherein the first correction function for the first color component is for gamma correction for luminance in the presence of signals for color components of the plurality of grays. 
   
   
     56. A method to generate correction functions for performing color correction for a device for signals of different color components in a color space, the method comprising:
 generating first correction functions for first color components in the first color space by reducing in a subspace of a second color space first differences between a target point and positions of a plurality of colors on the device corresponding to signals corrected by the first correction functions.  
 
   
   
     57. A method as in  claim 56  wherein the target point is a white point and the plurality of colors are a plurality of gray levels from a white to a black. 
   
   
     58. A method as in  claim 56  wherein the subspace is related to a chromaticity diagram. 
   
   
     59. A method as in  claim 58  wherein the first color space is a RGB color space; second color space is a xyY color space; and the subspace is a xy color space. 
   
   
     60. A method as in  claim 56  wherein said device displays colors; and wherein both luminance and chromaticity values relative to said device are used in reducing the first differences. 
   
   
     61. A method as in  claim 56  wherein said device displays colors; and wherein the first correction functions are generated by modifying values of several color components interdependently. 
   
   
     62. A machine readable media containing executable computer program instructions which when executed by a digital processing system cause said system to perform a method to generate correction functions for performing color correction for a device for signals of different color components in a color space, the method comprising:
 generating first correction functions for first color components in the first color space by reducing in a subspace of a second color space first differences between a target point and positions of a plurality of colors on the device corresponding to signals corrected by the first correction functions.  
 
   
   
     63. A media as in  claim 62  wherein the target point is a white point and the plurality of colors are a plurality of gray levels from a white to a black. 
   
   
     64. A media as in  claim 62  wherein the subspace is related to a chromaticity diagram. 
   
   
     65. A media as in  claim 64  wherein the first color space is a RGB color space; second color space is a xyY color space; and the subspace is a xy color space. 
   
   
     66. A media as in  claim 62  wherein said device displays colors; and wherein both luminance and chromaticity values relative to said device are used in reducing the first differences. 
   
   
     67. A media as in  claim 62  wherein said device displays colors; and wherein the first correction functions are generated by modifying values of several color components interdependently.